Field of the Invention
One disclosed aspect of the embodiments relates to a communication apparatus, a method for controlling a communication apparatus, and a storage medium.
Description of the Related Art
Demands for power saving have ever been increasing lately. In this context, many apparatuses have a mechanism of transitioning to a power saving mode and to a normal mode. The transition to the normal mode occurs when a job requiring the normal mode occurs. The power saving mode features a low power consumption amount in an unused state. The normal mode is an operating state involving a normal amount of power consumption. A dedicated remote controller has been widely used for remotely causing such an apparatus to transition to the normal mode, using an infrared communication function or the like. Some recently available apparatuses, with a network communication function using a wired local area network (LAN) or a wireless LAN, can be remotely transitioned to the normal mode using the network communication function.
Some apparatuses in the power saving mode transition to the power saving state with clock speeds reduced, so that all the functions can operate but with lower performance. Some apparatuses in the power saving mode have power and clock supply stopped to components other than a network communication function unit and have a memory only partially usable, for more power savings. In the latter configuration, a program size used in the power saving mode needs to be designed to be small, making only a part of the network communication function remaining active in the power saving mode.
A protocol known as Internet Protocol Version 6 (IPv6) features address autoconfiguration involving duplicate address detection. The duplicate address detection uses a solicited-node multicast address that is one of multicast addresses. The communication apparatus on a listener side uses a multicast group management protocol known as Multicast Listener Discovery (MLD), to use a multicast address. The communication apparatus on the listener side needs to notify a router or an MLD snoop switch of an intention to receive the multicast address, by using the MLD. The MLD includes functions of joining, maintaining, and leaving a multicast group. Multicast Listener Discovery Version 2 (MLDv2) further includes a function for managing an address indicating a multicast packet source.
Japanese Patent Application Laid-Open No. 2010-124331 discusses a technique related to operation control during the power saving mode. In Japanese Patent Application Laid-Open No. 2010-124331, a wireless communication function is turned ON and OFF at a predetermined interval during the power saving mode. An apparatus discussed in Japanese Patent Application Laid-Open No. 2010-124331 transmits a join packet using the MLD when the wireless communication function turns ON to receive the multicast packet while being in the power saving mode.
However, the apparatus discussed in Japanese Patent Application Laid-Open No. 2010-124331 transmits no join packet using the MLD while the wireless communication function is OFF. Thus, the apparatus discussed in Japanese Patent Application Laid-Open No. 2010-124331 might fail to respond to a packet for maintaining a multicast group, periodically transmitted by the router, when the wireless communication function turns OFF after the join packet has been transmitted to the router. If the packet for maintaining the multicast group is met with no response, it is determined that there is no listener node (apparatus). As a result, the multicast packet might be blocked (might not be transmitted) depending on a configuration of the MLD snoop switch provided between the apparatus and the router. In other words, the apparatus discussed in Japanese Patent Application Laid-Open No. 2010-124331 might fail to maintain the multicast group.
When the multicast packet is blocked during the power saving mode, the duplicate address detection might not work. When the duplicate address detection does not work, the network might fall in a state of having a plurality of apparatuses with the same IPv6 address, resulting in a failure to properly communicate using IPv6.
The MLD involves a large amount of functions and parameters. Thus, a large amount of resources is required to keep all the functions, required for maintaining the multicast group, active in the power saving mode.